The present disclosure relates to a retractable step. A retractable step is understood as meaning an entry aid for assisting the entering and exiting of vehicles, particularly rail vehicles. The retractable step has a surface which can be walked upon being extended from the vehicle essentially in a linear direction in order to bridge the gap between the vehicle and the platform or the like.
Depending on the positioning between the vehicle box body and the platform, the retractable step, generally toward the end of its extension movement, comes into the region of the platform . There is the risk of it moving laterally into the essentially vertically extending platform wall. This problem is overcome by sensors in the region of the leading edge of the retractable step.
Another problem is that, in the case of an extended retractable step, a change in height of the retractable step may occur during the time the vehicle spends in the station. This may take place within a short period by the suspension yielding, by the vehicle load changing as passengers get in and out, by the wind load stressing changing, and by more of the same sort of reasons. The greatest possible change in height is defined here by various parameters of the vehicle (type of suspension, position of the stops, length of the lever arms of the retractable step relative to the pivot axis, etc.) and is called maximum change in height below. The actual change in the height position within the context of this maximum change in height may result in luggage or passengers becoming trapped, or the retractable step being damaged if the retractable step is correspondingly lowered. Since the objects at risk generally do not extend over the entire width of the retractable step and it cannot be predicted in which region of the retractable step they are located, detection has hitherto been impossible and the risk of body parts or objects becoming trapped or of the retractable step becoming damaged has had to be accepted.
The present disclosure relates to a device with which it is possible to carry out a detection of the above-mentioned type in a satisfactory and cost-effective manner.
According to the present disclosure, this is achieved in that a strip is connected movably to the retractable step. The strip extends essentially over the entire length of the retractable step and, in the activated state, being located essentially under the front edge of the retractable step. In addition, at least one sensor is provided which detects the position of the strip and/or the force transmitted by the strip to the retractable step.
As a result, every impermissible approach toward the upper side of the platform can be detected as can the imminent risk of an object or body part becoming trapped. The positioning of the strip makes it possible, during the extension of the retractable step, also to detect the space (detection space) in which, during a lowering operation, the retractable step could move and thus makes it possible to safeguard it. An activated state is taken up by the strip at least during the extension of the retractable step.
The movable connection between strip and retractable step makes it possible to bring the strip into the desired position, if appropriate automatically, during the extension of the retractable step. The monitoring of this position remains activated during the extension of the retractable step into its end position.
If a change in the position of the strip is detected, the extension movement is stopped and the retractable step is moved back by a predetermined length by which a safe distance from the object is ensured. In addition, for example, an acoustic and/or optical alarm signal may be emitted. Of course, a different reaction is possible if this is desired by the operator.
The strip itself may either execute an extension movement which is oblique with respect to the direction of extension of the retractable step but is essentially linear. It may also execute a rotational movement and be swung out.
Depending in each case on the design and movement of the strip, a very wide variety of sensors, which can be designed as switches or strain gauges or based on an electrodynamic or piezoelectric effect, are suitable as the actual sensor. The sensors may be arranged either directly in the strip and measure the force between an underlying surface and the strip, or they are accommodated in the region of the bearings of the strip and measure the forces between the strip and retractable step, which forces may originate from the first-mentioned forces.
The transition of the strip from the passive position into the active position can take place by the dead weight of the strip, a slotted-guide mechanism and possibly a spring. Of course, it is also possible to provide a motor drive.
In accordance with the present disclosure, if the retractable step is to be retracted if a trapping risk is established, it is favorable that, during this retraction movement, the strip releases any objects already trapped as rapidly as possible without further loading and does not trap and keep hold of them.
Other aspects of the present disclosure will become apparent from the following descriptions when considered in conjunction with the accompanying drawings.